Private hunting operations in these countries control more than 540,000 square miles (1.4 million square kilometers) of land, the study also found. That's 22 percent more land than is protected by national parks.

As demand for land increases with swelling human populations, some conservationists are arguing that they can garner more effective results by working with hunters and taking a hand in regulating the industry.

Sport hunting can be sustainable if carefully managed, said Peter Lindsey, a conservation biologist with the University of Zimbabwe in Harare, who led the recent study.

"Trophy hunting is of key importance to conservation in Africa by creating [financial] incentives to promote and retain wildlife as a land use over vast areas," he said.

In an upcoming edition of the journal Conservation Biology Lindsey and an international team of colleagues call for a plan to increase the conservation benefits of sport hunting, including a certification program to more tightly regulate the industry.

"To justify the continued existence of [protected] areas in the context of increasing demand for land, wildlife has to pay for itself and contribute to the economy, and hunting provides an important means of achieving this," Lindsey said.

Hunting's Checkered Past

In order to be certified under Lindsey's proposed plan, hunting operations would have to prove their commitment to animal welfare, careful management of hunting quotas, wide-ranging conservation objectives, and the development of local communities.

"The time has come for greater scrutiny from scientists to promote maximum conservation benefits from hunting," Lindsey said.